Our previous work emphasizes that tissue outcome from experimental stroke is gender-dependent and influenced by cellular and molecular actions of female and male sex steroids. We have shown that estrogen provides protection from cerebral injury in rodents of both sexes, even in the presence of complicating stroke risk factors such as hypertension and diabetes and in aging animals. The overall purpose of this project is to further examine inherent sex-linked injury mechanisms with emphasis on the role of 17-beta estradiol and on the principal active androgens, testosterone and dihydrotestosterone. Estrogen' s mechanisms of protection are clearly multifactorial and involve both brain and cerebral vessels. Aim 1 will further evaluate the role of estrogen receptor (ER) subtype alpha vs beta in mediating estradiol's neuroprotective mechanisms. Our preliminary data that estradiol treatment can only partially protect ER alpha deficient mice (alphaERKO) from ischemic injury. We will test the hypothesis that estradiol does not protect alphaERKO from middle cerebral artery occlusion (MCAO) as compared to wild type or ER beta deficient (betaERKO) mice. In aim 2, we will evaluate the importance of estrogen's known activation of the PI3-Akt kinase signaling to the steroid' s neuroprotective properties in experimental stroke. The hypothesis is that estradiol treatment reduces delayed damage after MCAO through enhancement of the PI3-Akt pathway activation that ordinarily occurs after ischemia. Aim 3 will determine the contribution of estradiol aromatized from testosterone in brain to neuroprotection from focal cerebral ischemia and examine mice genetically deficient in cytochrome P450 estrogen aromatase vs treated with local brain aromatase inhibitors. Most research aimed at understanding gender differences in experimental or clinical stroke has focused on the potential value of female sex steroids. An equally important issue remains understudied, i.e. if and how androgens alter incidence and outcome from cerebrovascular disease. Aim 4 will determine if testosterone and dihydrotestosterone (DHT) play an important role in outcome from MCAO in adult and middle-aged male animals. Our preliminary data suggest that potent androgens enhance damage in young males but provide protection in middle age-stroke. The importance of androgens to stroke is virtually uncharted territory. These findings will have broad application to patients with brain injury from stroke or reperfusion injury after invasive neurosurgical procedures.